Baffle for boilers



Oct. 20,1925 1,557,874.

J. PR ENTICE BAFFLE FOR BOILERS Filed Feb. 15. 1922 e Sheets-Sheet 1.

' I NVE/YTOR.

W; I BY Ham ATTORNEYS.

Oct. 20, 1925 J. PRENTICE BAFFLE FOR BOILERS 1922 6 Shee tsSheet 2 Filed Feb. 15

INVENTOR.

Oct. 20, 1925.

' .1. PREN TICE BAFFLE FOR BOILERS 6. Sheets-Sheet 5 Filed Feb, 15, 1922 i /alas. V I M,

A I N VEN TOR.

M TTORNEYS.

Oct. 20, 1925- Q J. PRENTICE BAFFLE FOR BOILERS Filed Feb. 15. 1922 s Sheets-Sheet 4 Oct. 20, 925. 1,557,814

J. PRENTI CE- BAFFLE FOR BOILERS Filed Feb, 15, 1922. 6 Sheets-Sheet 5 I N VEN TOR. m

' r-HJL ATTORNEYS.

- Oct.- 20,1925 7 1,557,874

- J. PRENTlQ-E} BAFFLE FOR 'BOILBRS Filed Feb. 151 1922 s Sheets-Sheet. g;

Q INVENTR.

BY v

v ATTORNEYS..

Patented Oct. 20, 1925.

UNITED sr TES gPATENT OF IC -31f JOHN PRENTICE, orBAYonNn, new -JEeSEY,;ASS1G-m.em mrin'muaoocx & wILcox COMPANY, or BAYONNE, NEW JERSEY, a COBBQROATIONOF NEW JERSEY.

BArrLE FOB BOILERS.

Application filed February 15, 1922. SerialNo. 536,696. I

To all whom it may concern. 1

Be it known that I, JOHN PRENTIGE, a citizen of the United, States, residin at Bayonne, in the county of Hudson and tate of New Jersey,have invented certainnew and useful Improvements in Bafiies for Boilers, of which the following isa specifica; tion. V v t My present invention relates to battles arranged to extend across the water tubes of boilers, particularly where such tubes are horizontal and arranged in horizontal rows. It will be understood that in the term horizontal, I also include tubes which are horizontally inclined, as is the' usual practice. My invention also particularly relates to in clined cross bafiles in which the-battle is made up of bricks or tile.

My invention will be understood from the following description and the drawings, in which Figure 1 is a sectional elevation of a well-known type of water-tube-boiler, having horizontally inclined water tubes and-a cross baffle, illustrating one form of my invention, Fig. 2 is an enlarged section of a portion of the cross baffle shown in Fig. 1; Fig. 3 is a view of Fig. 2 looking from the right of Fig. 2 along the tubes; Fig. 4 is an enlargement of a bafile'similarto the inclined baffle shown in Fig. 1 showing a modification; Fig. 5 is a view of Fig. 4 look,- ing from the right of Fig: 1 along the tubes, with the tiles removed; Figs. -6, 7 and 8 are respectively cross section, elevation and plan of the form of backing plate section shown in Fig. 4; Fig. 9 showsanother embodiment of my invention as applied to aboiler of the type shown in Fig. 1; Figs. 10 and11 are' enlarged views of a portion of the incllned baflie' shown in Fig. 9, Fig. 10 being a section'of the lower part of such bafile,and Fig. 11 view from the right of Fig. 1f) lookingalong the tubes; Figs.12 and 13 are respectively side and end views o't-a portion of the tubes showing in more or less diagrammatic form the illustrated embodiment of the form of tile which I use; Figul t is similar to Fig. 12 showing a tile making a less angle with the tubes than does the tile "in Fig."12; Fig. 15 is a side elevation of my illustrative form of'tile; Fig. 16 is a view of such tile looking from the left of Fig; 15; Figs. 17- and 18 are respectively section and end views on a'largerscale, the section of br ne ta n 1 the lie? 17%? .91

Fig. 18, andFigs. 19and 20 are diagrams inatic views illustrating'the method of in serting the sectionsjot' the backingplate and the building up of a: tile wall in L front thereof. Corresponding reference characters refer to corresponding parts in theseveralviews. 7 Referring nowlto the arrangement shown in- Fig. :1, the boiler illustrated has the usual headers 10- and 11 and a steam drum 12, the

watertubes 13 extending between the headers and being horizontally :inclined. The form of boiler illustratedis of the so-c'alled Fdrop-leg construction; that is to say, the

tubes are divided into banks separated by a space with a plurality of-rowsof tubes in the lower bank, but the number of horizontal rows in the lower bank being much less in number than the horizontal rows in the. upper bank. The boiler is provided with a baffle 14 extending along'thelower tubes toward thecenter of the boilerand from. the inner end of the baffle 14 extending upwardly is an inclined baflie which I'have designated, generally, by the character. 15.

This crossbaflle 15 isnot only inc-linedzto the tubes themselves," but is inclined to the vertical, so that, unless such tendency is overcome, it would fall forwardly or to the right of Fig.1. The. pass across the tubes defined by the headers 11 and the inclined baffle 15 is a constantly decreasing one, and the gases after passing. across the tubes may flow-over a superheater, as illustrated, and then downward at the left of the battle 15 and between it and a vertical baffle 16. The

ases' then flow upward betweenfthe headers 10 and the bafile 16 to the "gas outlet.

Because the hottest gases pass 'thro'u h the first passbetween the bafile 15 and t e headers 11, it is desirable that the face of the baffle 15 adjacent this pass shall be made. of some heat resisting material,.and :I use tile or brick for this purpose. For some purposes, it is desirableto provide a so-called backing plate for the tile; wall or walls of the bafiie, and this plate may be of cast iron. It will also be understood that not only must the bafilelbe one which will resist, so far as possible, the action of the heat, but it should be capablev of being putf'in position without undue labor after the boiler has been erected, and furthermore, it should be of such a character that any portion of it y be raters! er reread are t e e a 9 bottom section.

has been in operation. The arrangement which I have provided accomplishes all of these purposes. In the arrangement shown in Figs. 1 to 8, inclusive, a backing plate :made up. prefer ably of cast iron or other metallic sections is built up across the tubes at the angle which it is desired that the bafiie shall make with the tubes. The greater portion of the backing plate ismade up of sections 17 having recesses 18 along the top and bottom edges-of the section, which recesses are arranged tofit around the tubes. The sections arealso provided, in the form illustrated, with recesses or interlocking offsets at the top an'dbottorn, as at 19, 20, and the section 17 is'designed so that when placed in posi- .tion, as best shown in Fig. 4, each of the recesses 18 will fit snugly around the tube. The length of the section may be as great as desired,v but preferably in a boiler of ordinary width,' there will be a plurality of sections placed end to end to cover the entire width of a horizontal aisle in the boiler.

t As sho-wn-in'Fig. 5, the tubes, in the illustrative boiler, are arranged in staggered relation so as to form horizontal and diagonal aisles. I

Where there is, a greater distance between adjacent horizontal rows, the sections 17 are made correspondingly wider, as will be obvious; .Such a plateisshown at 21 where a horizontal row of-tubes has been omitted.

Aswillbe seen from an inspection of Fig. 4,-therecesses 19 and 20 are interlocked so that if any section 17should tend to ,rota'teto the right ofzFig. 4:, as it would be pulled by. gravity, suchrotation would be resisted by thecontact. of its lower edge with the upper edge ofthe next lower section 17 and by thecontact of its upper edge 19 with the. lower edge of the next higher section. In other words, no section 17 can fall fore ward, so long as the lowermost or the uppermost section. is held against rotation. As shown in Figs. 2fand 41, the lowermost plate, which extends across the space between the upper. and lower banks of tubes, is anchored on backed up to preventits falling forward. In the form shown inrF-ig. 2, the plate 22 has afoot at an, angle. to. the-main body of, the plate-v .22, which foot iS contacted by -21 portion of the horizontal baflie ,1t. In the arrangement'shovvn in Fig.- 4, each plate 23v is connected to; a strap 24: attached to one of, the tubes, If desi d the turning of the individual sections, may be prevented by anchoring the :top section instead of the f The. backing plate made up of the interlo eked plates, such as '17 and-21, is held in P si i-Q le si i a y. of he at tub r backing ar Th se bait t nd through the diagonal? aisles of the tubes and are held against movement longitudinally of the tubes by clamps 27 attached to the tubes. Each section 17 is contacted by at least one of the bars and, as illustrated, each section restsagainst at least two of the bars for greater stability. The wide sections, such as 21, may be contacted by cross bars 26 extending through slots in the ends of the bars to hold the plates 21 more certainly against motion longitudinally of the tubes.

In the form illustrated, the tile or brick walls in front vof the backing plate and constituting the remainder of the baflle, are shown as two in number,'though it will beunderstood that any number of such walls may be used, as desired.

Each wall is made up of a plurality of tiles 28 set edge to edge, each tile being preferably of the form illustrated best in Figs. 15' and 16, and being substantially quadrilateral in elevation with a tube recess at each angle of the quadrilateral. These tile are arranged so that, when-in position as shown in Fig. 15, preferably the entire width of the tile will contact with each tube throughout the entire extent of the tube recess. Since usually the baflie will make an angle with the tubes, the side walls of the tilexwill necessarily make a corresponding angle with the face of the tile. 'The tiles are arranged to beinsertedso as to occupy the position shown best in Fig. 13, with two of the edges of the quadrilateral horizontal and the two remaining edges substantially parallel to the diagonal aisle. As will be seen in Fig. 13,, the edges of each tile are contacted by edges of adjacent tile-s for the full thickness of the tile and, by reason of the snug fit of the tilearound the tubes, a single wall will provide a comparatively tight bafile, and' yet one which can be mounted or demounted from position after the boiler has been erected. 3

.The tiles illustrated are constructed in such a waythat, after they are in position, there Will be no tendency for'the individual tile to topple forward or to the right of-Fig. 12, the direction in which the inclination of the baffle would apparently cause such tile to fall. signing each tile so that as it rests in the position shown, for instance, in Fig. 12, a vertical line dropped from the center of gravity will pass to the left ofthe line of contact between the tileqand the tubes on which it rests. Consequently, the tendency for the tile. is to rotate counterclockwise in. Fig. 12, and thus hold the tube recesses of the tile snugly against the tubes. The same description applies to Fig. 14, in which the tile shown at a less angle to the tubes than in Fig. '12. It will be obvious by a comparisonof Figs. 12 and 14 that the thickness of the tile may be less in the inclination I accomplish this result by deshown in Fig. 14 than in the inclination shown in Fig. 12. In other words, in'Figj 14,'the tile may be thinned until its front.

edge, reaches the intersection. of the vertical line from the center of gravity withflthe top of the tubes, and yet the tile will have no tendency to fall to the right of Fig. On the otherhand, ifv a greater inclination; to the tubes than that shown in Fig. 12 is desired, it will be obvious that the'tiles will have to be thickened accordingly, in orderto maintain their individual stability, if gravity alone is to be utilizedto-hold the tile in place. By a proper coordination of the thickness of the tile and the desired angle of the inclination of the baflie, I am enabled to provide a tile which will contact for its entire width with the tubes and yet may be readily inserted in place. This is illustrated best in Fig. 15, where the tile has been ro tated into position by turning on the axis X extending through the line of support between the tile and the tubes on which it rests. It will be obvious that all points of contact betweenthe upper tube to the right of a vertical line from the point X will move away from that tube when the tile-is turnedcounterclockwise; In the form shown in Fig. 15, a very small portion of the tile is shown at the right of such vertical line from the point X, but it'will be obvious that such portion is so near the Vertical'line that substantially all of such points would also move along the tube 15 and then away therefrom. Therefore, such a tile may'be rotated into posit-ion practically without springing the tubes, While, preferably, 'I arrange the tiles so that they 'contact'with the tubes for their full width, itwill be understood that for some purposes this feature may be modified by arranging the tile so that a portion of each edge must be cut away to permit the tile to be turned into place, thereby reducingthe contacting por tion between the tile and the tube;

In the form illustrated, the tiles are pro vented from falling 'by contact with the backing plate. This is best shown in Fig. 17. Since the normal from the point on which the tile must turn is shorter than the line of Contact of the tile with the tube, any turning of the tile "from the full line to the I dotted line position of Fig. 17 will result in a bodily motion along the tube which, of course, will be resisted by the friction between the tile and the tube and also when the tubes are inclined to the horizontal, by gravity, since such motion would result in a shifting of the tile bodily upward along the tube. p In order to make a tightbaflie, I preferably'provide at least two walls of tile. As illustrated in Fig. 13, the wall next to the backing plate is made up of tile in which the long diagonal is inclined to the left of that figure. The front wall,.on the other hand, is made up of tile in which the diagonal extends to the right: in Fig 13, and the tiles in 'the front wall are arrangedin rela-: tion to the tiles in the rear wall in such a way that the joint betweenthe sides of: the. tiles in the rear wall lie behind the solid: porti'onof the corresponding tiles: in-the front wall. Similarly, the joints; between the sides of the tiles in the front :wall'lie opposite the solid portion of the tiles in the rear wall. This arrangement nbr'eaks th'e jointsbetween the sides of the. tile. 'Simi-. l'arly, inthe form illustrated in Figs. 1 0,111 and'13, the upper horizontal edge of; each tile in the front wallis higher than theup per edge of the corresponding tile in the rear wall', and similarly,:the lower edgeof each-tile in the frontwall is higher. than the lower edge of thecorresponding'tile'in the rear wall. This arrangement breaks the joints between the top, and bottom edges of the tile. Consequently, with two walls of tile, the jointsbetween the tile are broken so that a relatively tightbaffie is provided by the v, tile alone, and this tightness is rein forced by the backing plate because of the overlapping of the edgesiof theisectio'ns thereof, which are'als'o arranged so that the joints thereindo not comeopposite any-of the joints in the rear wall of the tile. Since the two walls of tile; are in 7 contact with each other and the rear wallof; tileyis'in contact with the backing plate, any tendency of each tile tofall forwardly in the direction of the inclination of the baffle is prevented by the fact that a portion of each tile extends below the line of contact between. thefront face of the tile and the tubes 0'11. which it rests. clockwise, as illustrated in Fig. 17' by dot: ted lines, the partbelow the line of support will resist such turning, by reason of its con tact either with the other wall 'of tile or with the backing plate, as the case may be. 'In other words, in order to turn the tile 28 from the position shown in Fig. 17in full lines,-it will be necessary to-move the tile bodily along'the tubes, and when the tubes are inclined to thehorizontal, as illustrated, such a motion would be. resisted by gravity whichtends to cause the tile to slide down. the tubes to. remain in contact with the backing plate or the other wall of tile. One of the advantages ofthe arrangement which I have illustrated resides in the fact that, because of the horizontal inclination of the tubes, all'parts of'the bafiieltend to slide downthe tubesg'andthereforeflco hold the severalparts together in the position'shown in the several figures, an'dthus hold the several parts in such position that no one of them will'fall out. of place. By reason of the attachment of the backing bars to the tu e he b tt e s e h d s' ed Consequently, if the "tiliexis tilted position against this tendency to slidedown the tubes.

In Figs; 19 and20, I have illustrated a method by which the baflle may be built in place. The backing bars are first, placed in position and attached to the tubes by the clamps 27. Then the backing plate is built up sectionb-yseotion beginning at the bottom, each section being inserted lengthwise down a diagonal line, as shown in Figs. 19 and 20 at 171. Then the section is turned endwise into the position indicated at 1.72, and then the section is rotated on its long axis into the position 173'. Now the section isagain turned fiatwise into the position,

shown at 174, from which position it may be turned through the position 17 5 until the recesses are in contact with the tubes, and

the section is, then slid into position i 5 against the backing bars 25. Similarly, the

tile walls are built up beginning at th bottom, each tile being passed fiatwisethrough a diagonal aisle and then turned until it lies in a position shown in-dotted lines at 28.1

of Fig. 17, from which 'it maybe rotated into itslposition against the backing plate.

In the tube. arrangement shown in Fig. 13, it will be seen that. the tubes inthe horizontal rows'are staggered in such a manner that a straight diagonal line cannot be drawn through all of the tubes. For this reason, each wall will have two shapes of tile, differing slightly to take care of this particular arrangement. If, as is sometimes the case, the tube arrangement were such that adiagonal line could be passed through the centers. of'all' of the tubes along a diagonal aisle, then each Wall would have one form of tile only.v

Because'the lower bank in a drop-leg con struction usually has a comparatively small number of horizontal rows of tubes, it is desirable to support the baffle in such a way that the weight is carried by thelarge number of rows in the upper bank. To this end, I provide means by which the tile forming part of the bafile' which extends across the space in the drop-leg construction shall be supported onthe backing plate, and so that the part of the backing plate, extending across this space shall be suspended from the upper bank of tubes. In the form' illustrated in Figs. 4'and 5., the plate 23 is suspended froni the clamps 24, each of which surrounds one of the tubes in the upper bank. lTlie plate. 23 has pins 29 attached thereon andlocatedon centers. correspond. ingto the centers of the tubes. On each of the. pins '29 may be supported a round piece 30 0f the same diameter as the tubefthis piece 30' maybe either of refractory material. or of; metal. It will be obvious, therefore, that the: tile walls extending across the space between the two banks. oftubes can be built up. preciselythe same as on the tubes themselves, the same shapes and sizes of tile being used and the weight of such tile will bev carried through the pins 29 to the plate 23., and from there to the tubes of the upper bank. I V

Instead of the arrangement of dummy tube centers shown in Fig. 4, I'may provide the arrangement shown in Figs. 10 and 11, in which metallic or refractory pieces 31 of the same diameter as the tubes and arranged on similar centers, are held to the backing plate 32 by bolts 33, the tile being mounted on these dummy portions of tubes similar to the way in whichthe tiles are mounted on the'tubes themselves; In this arrange-.

ment, the plate 32 is not suspended from the upper tubes, but obviously provision to that end may be made, if desired, in any suitable manner, as for instance,-that illustrated in Fig. 4. For instance, the system of backing bars may be supported from the top ofthe backing plate as by a hook 34 (Fig. 4) and the plate 32 may be connected to the system as shown in Fig. 10. Because of the cross bars 26 extending through slots in the bars 25, the entireweight of the backing bar system and anything attached thereto will be carried on the backing plate and thus dis tributed over the entire upper bank of tubes 13.

'While I have shown my baflie in its preferred form, it will be understood that many of the details maybe varied within wide limits. It will also be obvious that certain features of my inventionmay be used alone or in combination with other arrangements. It will also be obvious that, while the b'aflie which I have described is particularly adapted for inclined cross baffles, many of its features will be useful in vertical baffles, particularly where the horizontal tubes are inclined.

I claim I 1. An inclined cross bafiie for water-tube boilers having horizontally inclined tubes arranged to form horizontal and diagonal aisles, having tiles each substantially quadrilateral in elevation and having. a recess at each angle of the quadrilateral, each recess being adapted, to fit snugly around a tube the entire thickness ofthe tile, with two of contact of the front face of the tile with the two tubes on which it is supported.

3. Aninclined cross baffle for water-tube boilers having horizontally inclined tubes arranged to form horizontal and diagonal aisles, having tiles each substantially quadrilateral in elevation and having a recess at each angle of the quadrilateral, each recess being adapted to fit snugly around a tube the entire thickness of the tile, with two of the sides of the quadrilateral horizontal and the two remaining sides substantially parallel to a diagonal aisle, said tile being constructed and arranged so that, on being turned from its normal position on the line of contact of its front face with the two tubes on which it is supported, all parts of the tile recesses will move away from the parts of the tubes with which they are in contact when in normal position.

4. An inclined crossbafile for water-tube boilers having horizontally inclined tubes arranged to form horizontal and diagonal aisles, having tiles each substantially quadrilateral in elevation and havinv a recess at each angle of the quadrilateral, each re cess being adapted to fit snugly around a tube the entire thickness of the tile, with two of the sides of the quadrilateral horizontal and the two remaining sides substantially parallel to a diagonal aisle, with the center of mass of the tile in the rear of the line of contact of the front face of the tile with the two tubes on which it is supported, said tile being constructed and arranged so that, on being turned from its normal position on the line of contact of its front face with the two tubes on which, it is supported, all parts of the tile recesses will move away from the parts of thetubes with which they are in contact when in normal position. i

5. In an inclined cross baflie for watertube boilers having horizontally inclined tubes arranged to form horizontal and diagonal aisles, a pair of contacting walls, each composed of tiles placed edge to edge, each tile being substantially quadrilateral in elevation and having a recess at each angle of the quadrilateral arranged to fit around a tube, with two of the sides of the quadrilateral horizontal and the two remaining sides substantially parallel to a diagonal aisle, the tiles in the two walls being arranged so that no joint between the tiles of one wall is opposite a joint between the tiles of the other walls.

6. In an inclined cross baffle for watertube boilers having horizontally inclined tubes arranged to form horizontal and diagonal aisles, a pair of contacting walls, each composed of tiles placed edge to edge, each tile being substantially quadrilateral in elevation and having a recess at each angle of the quadrilateral arranged to fit around a tube, with two of the sides of the quadrilateral horizontal and the two; remaining sides substantially parallel to a diagonal aisle,

rilateral horizontal and the two remaining sides substantially parallel to a diagonal aisle, the long diagonals of the tiles in one wall extending in the same general direction and at an angle to the diagonals of the tiles in the other wall, and the top horizontal edge of each tile in one wall being higher than the top horizontal edge of' the correspondingtile-in the other'wall.

8. In an inclined cross baflie for watertube boilers having horizontallyinclined tubes arranged to form horizontal and diagon-al aisles, a backing plate comprising a plurality of sections, each extending across and filling at least a partof a horizontal aisle between adjacent rows of tubes, with tube recesses at the top and the bottom of each section and the sections being placed edge to edge, and backing bars located in the diagonal aisles and attached to the tubes and contacting with the rear of the backing plate, each section of the backing plate contacting with at least one bar.

4 9; In an'inclined cross bafflefor waterlZIlb e bOll81S having horizontally inclined tubes arranged to form horizontal and diagonal aisles, a backing plate comprising a plurality of sections, each' exten'ding across and filling at least a part of a horizontal aisle between adjacent rows of tubes, with tube recesses at the top and the bottom of each section and the sections being placed edge to edge, and backing barslocated in the diagonal aisles and attached tothe tubes and contacting with the rear of the backing plate, each section of the backing plate contacting with at least one bar, one of the horizontal edges of each section having a portion overlapping the horizontal edge of the adjacent section.

10. In a cross baflle for water-tube boilers I having horizontally inclined tubes arranged in horizontal rows, an inclined backing plate extending across the tubesand comprising a plurality of sections placed edge to edge, each section having tube recesses at the top and at the bottom and extending across and filling at least a portion of a horizontal aisle between adjacent rows of tubes, the

sections at one edge of the plate being anchoredto prevent such sections rotating on the tubes on which they rest, and other sections resting on the tubes and unattached to the tubes or the sides of the setting with" the quadrilateral arrangedto fit around a tube, with two of the sides of the quadrilateral horizontal and the two remaining sides substantially parallel to. a diagonal.

.aisle, e-ach tile having a part below-the line of contact between the front face thereof and the tubeson which it rests, whereby the turning of the tile. on said line of contact is prevented by the backing plate.

12.. In an inclined cross battle for watertube boilers having horizontally inclined tubes arranged to form horizontal and diagonal aisles, a backing plate extending across the tubes, and a pair of walls of tile in front of the plate, with the rearinost Wall in contact with the plate and the; front wall in contact withthe rear wall, each'wall comprising tiles, each substantially quadrilateral in elevation and having airecessat each angle of the quadrilateralarranged tojfit around a tube, with two of the sides of. the quadrilateral horizontal and the two remaining; sides substantially'parallel to a diagonal'aisle, each tile having a; part below the" line of contact. between the front face thereof andthe tubes on which it rests,

whereby the turning of the tile on said line of contact is prevented by thebacking plate or the wall with which thetile contacts.

13. In a water-tube boilerhaving horizontally inclined tubes divided into two banks, with a spacebetween the banks, a cross baffle Q-XtGII'dlIIg ZIGIO-SS" the tubes of the/upper bank andthe space between" the banks, and means to support from the tubes of the upper bank, the weight of the portion of the baffle extending vacross said 14. In a water-tube boiler having hori; i

said baflle comprising a backing plate and i one or more walls of tile, said ba'cking pl-ate having a section extending across said space and supported on the tubes of the upper banks and the tiles in the portion of the walls extending across said space being supported by said section.

15. In a Water-tube boiler having horizontally inclined tubes divided into two banks, with a space between the banks, a

cross baflie extending across the tubes of the upper bank and the space between the banks, said battle comprising a backing plate and one or more walls of tile, said backing plate having a section extending across said space and supported on the tubes .7

of the upper bank and provided'with projections similar in diameter and arrangement to the tubes of the upper bank, and the tiles in the portion of the'walls extending across said space being similarin shapeg Y and size to the tiles forming the remainder of said wallsa'nd supported on said pro- Jeetions.

16. In a water tube boiler having horizontally inclined tubes divided intotwo 7 banks, with a space between the banks, a cross bafiie extending; across the tubesef the upper bank and the spacelbetween the banks, said battle comprising a backing plate and one-;or more wallsxo'f tile, said backing platehaving a section extending across said space and provided with pro- 1 jections similar in diameter and, arrangement to the tubes of the; upper bank, and the (files in the portion of the walls extend.- ing across said space being similar in, shape and size to the tiles forming the remainder of said walls and supported on said projections 1 JOHN PnENrIoE; 

